Conventionally, an engine with a turbocharger is known, and in this type of engine, the boost pressure of the turbocharger is suitably adjusted corresponding to an operating state of the engine.
For example, an exhaust passage of the engine according to Patent Document 1 is provided with a bypass passage that bypasses a turbine of the turbocharger, and a bypass valve is provided to adjust a flow rate of exhaust flowing the bypass passage. In this engine, the boost pressure of the turbocharger is adjusted by controlling an opening degree of the bypass valve.
More specifically, the control device of the engine according to Patent Document 1 functions appropriately by switching a feedback control, which controls the opening degree of the bypass valve corresponding to a deviation between an actual value and a target value of a pressure ratio before and after a compressor of the turbocharger, and a non-feedback control in which the deviation is not taken into consideration. Then, when switching from the non-feedback control to the feedback control, the deviation between the actual value and the target value becomes large, and an integral term may be large, so the control device sets the integral term to zero. Accordingly, overshoot or undershoot of the boost pressure is reduced.